Aluminum conducting surface treatment



ALUMINUM CONDUCTING SURFACE TREATMENT Filed lay 3, 1945 In waIIIIIIJIIIII III] Ill Zint-Peirdlalam 122/ M1 AT OR EY Patented July 1,1947 ALUIVIINUM CONDUCTING SURFACE TREATMENT Wilhelm Friedrich Bonwitt,Mount Vernon, N. Y., assignor to Burndy Engineering Company, Inc.,

3 Claims.

My invention relates to a method for treating aluminum conductors and/orconnectors to increase the electrical joint efficiency of the connectionbetween the two. This application is a continuation-in-part of myapplication entitled Aluminum conductor surface treatment," filed June26-, 1943, Ser. No. 492,416.

In my earlier application I disclosed a method 01 treating aluminumsurfaces by first applying concentrated nitric acid to the surface,drying the treated surface by air, and thereafter covering the surfacewith a zinc-petrolatum coating.

In the present application I have discovered a corporation of New YorkApplication May 3, 1945, Serial No. 591,813

that the electrical resistance of the connection canbe reduced,especially where a stranded aluminum cable is employed, by just coatingthe strands of the cable with the zinc-petrolatum.

Accordingly the primary object of my invention is to provide a method oftreating aluminum conductors, and/or connectors, so that a connectioncomprising a connector secured by pressure to an aluminum conductor willhave an electrical resistance equal to or less than an unbroken cablehaving the same length as the combined connection.

Another object is to provide a method of treating such a connectionwhere the conductor comprises a stranded aluminum cable.

I accomplish thee and other objects and obtain my new results as will beapparent from the device described in the following specification,particularly pointed out in the claims, and illustrated in theaccompanying drawing in which:

Fig. 1 is an exploded side view of a piece of aluminum stranded cableand an electrical terminal connector, shown in section and filled withzinc-petrolatum.

Fig. 2 is a side view showing in section the final connection.

In the drawing, reference numeral l0 designates an aluminum terminal,having a tongue section II provided with an aperture 12, and a barrel[3, having a bore i4 sufilcient in diameter to receive an aluminumconductor designated as I5, composed oi strands H5.

The bore i4 is completely filled with zincpetrolatum IT, a mixture ofmetallic zinc dust suspended in a heavy petrolatum jelly, and when aconnection is desired, the cable I5 is inserted 'into the bore of thebarrel, forcing the zincpetrolatum to completely fill the interstices ofthe cable end. The final indentation of the barrel as shown by referencenumeral I8, results in a final connection that has approximatelyone-half the electrical resistance of the untreated connection.

This has been brought out by tests in which untreated connections werecompared to connections that were treated in the foregoing manner.

For a pair of terminals indented to the ends of short lengths of No. 4aluminum aircraft cable to form jumpers having an overall length of 2%",the resistance in microhms for the untreated connections was 91.92.Where the cable ends were treated with the zinc-petrolatum theresistance was 69.57. In other words, the relative conductivity inpercent had increased from 88.9 to 117.5.

The improvement can be attributed to the method of treatment alone sinceall other variables such as size, stranding of cable, size of terminal,depth of indentation, length, etc., were kept constant.

Thus, starting with exactly the same cable, terminal, and indentation,the electrical conductivity of the finished connection can be increasedby one-third by the addition of the zinc-petro- -latum treatment alone.

In addition to providing lower initial resistance, the zinc-petrolatummixture helps to inhibit corrosion of the cable connection as waspointed out in my earlier application. The tests made show, afterconsiderable exposure, a relatively small increase in resistance of thetreated connections, as compared with the larger increase in resistanceof the untreated connections.

The zinc-petrolatum having considerable zinc dust contained therein, thepressure of the indented connection is apparently suillcient to causethe zinc dust to penetrate the oxide film formed on the aluminumsurfaces and to furnish a conducting path from aluminum to aluminumthrough the zinc particles. Where stranded cable is used, and the zincpetrolatum is forced between the ends of the cable strands, theparticles of metallic zinc coating each strand, break through the filmof oxide and thereby provide numerous low resistance current paths fromstrand to strand, and from strand to connector. This effecti'velyreduces the transverse resistance between strands, and prevents thecable from operating as a series of parallel conductors having highresistance between them.- Moreover the zinc-petrolatum prevents andinhibits the formation of oxides and other products of corrosion in theelectrical connection after it has been made and is in actual use.

Where a terminal is provided with an open back, it is important totemporarily close this second opening while inserting the cable, inorder to prevent the zinc-petrolatum from escaping from the open backinstead of penetrating the stranded cable end. This temporary blockingof the open back may be accomplished by covering the second opening witha finger during the insertion of the cable.

It is possible to use a metal other than zinc. and a binder other thanpetrolatum. A metal to replace zinc would have to be close to zinc inthe galvanic series. Such a metal would be cadmium, magnesium, etc. Thesubstitute for petrolatum would have to be some unctuous substance,nondrying, and have the consistency of substantially that of petrolatumat room temperature. Many wax or wax-like substances have theseproperties,

When convenient, the contacting connector may be cleaned by degreasingusing Oakite, etched by a trisodium phosphate solution, bright dipped indiluted nitric acid and zinc flashed. Other materials may be used toaccomplish these operations. Some additional improvements in theelectrical and corrosion characteristics may be thus obtained.

I have thus described my invention, but I desire it understood that itis not confined to the particular forms or uses shown and described, thesame being merely illustrative, and that the invention may be carriedout in other ways Without departing from the spirit of my invention,and, therefore, I claim broadly the right to employ all equivalentinstrumentalities coming within the scope of the appended claims, and bymeans of which, objects of my invention are attained and new resultsaccomplished, as it is obvious that the particular embodiments hereinshown and described are only some of the many that can be employed toattain these objects and accomplish these results.

I claim:

4 1. An electrical connector having a. tubular body for inserting analuminum conductor therein, said body completely filled with a materialcomprising a mixture of an unctuous substance with fine metal particlestaken from a group WILHELM FRIEDRICH BONWI'IT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,863,429 Willmore June 14, 19321,548,552 Prax Aug. 4, 1925 2,038,535 Brenizer Apr. 28, 1936 FOREIGNPATENTS Number Country Date 363,075 Great Britain Dec. 17, 1931

